This invention relates generally to master cylinders used in brake systems and more specifically to a plastic master cylinder for use in hydraulic brake systems.
Master cylinders are components used in hydraulic brake systems. Typically they include a reservoir and a cylinder body. The reservoir portion sits above the cylinder body. The reservoir contains a supply of hydraulic fluid. Orifices connect the reservoir portion with the cylinder portion to permit the hydraulic fluid to flow between the reservoir and the cylinder. The cylinder contains a piston that moves back and forth within the cylinder to pressurize the hydraulic fluid in order to activate the brake system. The cylinder and the reservoir may be molded as a single piece of metal, or, they may be separate pieces.
In the past master cylinders, particularly those used in surge brake systems, have been made of cast iron or aluminum. One problem associated with such systems is that they are susceptible to corrosion. The corrosion can contaminate the brake fluid causing excessive wear of brake components. In severe cases, the corrosion may cause leakage of brake fluid, and failure of the brake system. The cylinder portion of metal master cylinders typically must be machined to meet the tolerance requirements of brake systems, which adds to the expense in manufacturing such devices. An additional drawback is the heavy weight of metal parts. Often times metal master cylinders are treated with a rust preventative, which adds to the cost of manufacture.
An additional problem with standard master cylinders are xe2x80x9cgeysersxe2x80x9d that can occur during bleeding of the brake system. Residual pressure in the system can cause the brake fluid to shoot up through the ports between the cylinder and the reservoir, often shooting several inches above the master cylinder. This is messy, can damage components surrounding the master cylinder, and can even be dangerous if the brake fluid gets in the eyes of the person who removed the master cylinder cap.
The reservoir portion of master cylinders, especially metal ones that are formed as a single piece, are typically opaque. The level of brake fluid is checked using a dip stick, or a visual inspection of the inside of the reservoir. It would be preferable to be able to check the fluid level by a visual inspection of the outside of the master cylinder without the need to remove the cap, or use a dip stick.
These and other difficulties are overcome by the present invention.
Accordingly, it is a primary object of the present invention to provide a master cylinder wherein the reservoir and cylinder portions of the master cylinder are molded as a single piece of plastic.
It is a further object of the present invention to provide a master cylinder wherein the bore portion of the cylinder is formed during the molding process without any need for secondary machining.
It is an additional object of the present invention to provide a master cylinder that permits the level of hydraulic fluid in the reservoir to be observed through a sight gauge molded into the reservoir, without removing the cap of the master cylinder.
It is another object of the present invention to provide a master cylinder that deflects geysers that can occur through the replenishing port.
It is yet another object of the present invention to include a baffle that deflects geysers that can occur through the replenishing port and retain a float in alignment with a sight window to permit a determination of the level of hydraulic fluid in the reservoir without removing the reservoir cap.